Up to the Challenge

After deducing the operating principle of the lever, Archimedes declared, “Give me a place to stand and a lever long enough, and I will move the world.” After more than two millennia of progress, Chrysler debuted their 426 Hemi engine. It’s a heck of a lot more exciting than a long stick, and in the proper tune it churns out earth-moving quantities of torque. The only place old Archie would need to stand is on the gas pedal.

In the racing world, torque doesn’t get quite as much publicity as its sexier sibling, horsepower. After all, horsepower comes from elegant, high-revving powerplants that sing mellifluous arias. Engines that focus on torque tend to blurt out noises that have more to do with Armageddon than the opera.

Torque is a key component in the calculation of horsepower, however, and given enough twisting power, an engine doesn’t have to spin to 15,000 rpm in order to propel a race car with gusto. In fact, a slower-spinning, torquey engine can do the same job with far less mechanical stress, since the pistons don’t have to change direction 300 times every second.

At the Grassroots Motorsports 2009 Ultimate Track Car Challenge at Virginia International Raceway, a wildly mixed field of track-assault contraptions gathered in pursuit of a magic fast lap. Downforce, turbos, all-wheel drive, exotic carbon fiber panels and tightly wound race engines could be found throughout the field, as modern technology was abundant.

Glenn Bunch’s 1974 Dodge Challenger seemed to be an anachronism among the entrants—a vintage racing novelty—until the moment driver Phil Currin started cranking out hot laps. Jaws dropped as this ancient Hemi-powered monster shattered the 2:00 lap barrier. It eventually barreled to a class victory and a third-place overall finish, its wake littered with gasping, bewildered owners of more exotic machinery.

The Challenger is all the more impressive because it was built almost entirely by Glenn’s own hands. This machine hails from the glory days of IMSAGT racing. While the Porsches might have dominated the headlines of the day, the grids still featured a ton of innovation—like pony cars powered by big-block engines.

A Young Man’s Racing Primer

Glenn Bunch has been a car builder and racer for several decades, but don’t let the Challenger fool you: He wasn’t really raised as a muscle car guy. In the late 1950s, when he was still just a child, Glenn and his family resided in England. Glenn’s father, a sergeant in the USAF, owned a Jaguar and a Sprite during their stay in the British Isles.

“My dad would take me out to the abandoned airport strips and let me slide around when I was 10 years old,” recalls Glenn. “He’d tell me to poke the brakes hard while cornering fast and the tail would come out. It was a wonderful time—he was teaching me car control.”

Glenn’s car education wasn’t limited to shenanigans on abandoned airfields, as England in the late 1950s and early ’60s was a hotbed of sports car activity. Young Glenn was able to visit the places and personalities behind names like Elva, Cooper and Healey. He lived down the road from the Lister shop, and he’d politely walk around and see firsthand how sports cars were made.

The roadsters were cool, but Glenn became infatuated with his dad’s sleek and powerful Jaguar sedan. “Sedans are such a great, fun thing to watch,” he explains. “My dad bought a Jag sedan in England. You weren’t going to get passed by anybody in England unless it was another Jag; there was a pecking order. It was great fun. Those little back roads were 12 feet wide—the way the Romans built them—and the pavement was so smooth you didn’t need a good suspension.”

Glenn returned to the States and got involved in amateur motorsports, autocrossing and then road racing. He started with a Saab Sonett before graduating to a Jaguar XKE. He had fun in the Jag, but before long the Datsun Z-cars became the dominant force in the SCCA. Keeping the Jaguar competitive for SCCA sprint races turned into a prohibitively expensive proposition. Luckily, another organization saved the day.

“Along comes IMSA,” he says. “Run what you brung.” The International Motor Sports Association’s liberal rule set and long-form enduro racing welcomed cars of many types, and Glenn took the opportunity to get hours of track time in a single weekend in his Saab and Jaguar. He fixed wrecked cars at night to make money to support his racing addiction. “I had the best seat in the house,” he figures. “It was wonderful. All these guys I’d read about—it was a mind-expanding honor to be there.”

Heavy Metal

Glenn eventually decided he wanted something relatively inexpensive that could run closer to the front of the pack. IMSA’s All American GT category popped up in 1974, and Glenn decided that he knew enough about cars to build his own V8 creation for the new series. The Porsches had become the overdogs of GTO, so this new AAGT class was seen as a place for everything else, from the wild Dekon Monzas to home-built machines like Glenn’s.

Glenn saw how the small- and big-block Chevys had trouble keeping up with the Porsches. He figured that following the trend, IMSA would eventually open up the rules. In Glenn’s mind, allowing the turbocharging of high-displacement motors was inevitable.

He decided that a big-block Chrysler 426 Hemi would be the ultimate setup once turbocharging became legal. Since Glenn loved big, closed cars, he settled on a 1974 Challenger as his starting point. (The rules never did evolve to allow turbocharging over 350 cubic inches, however.)

Glenn’s first attempt at constructing an AAGT Challenger, built entirely from scratch save for the IMSA-required stock roof panel and doors, took nearly a year to complete. He solicited advice and parts from a variety of sources, and after some back-and-forth with IMSA on the legality of the car’s stance, he ended up with a somewhat exotic combination. While the engine featured some one-off engine components, Glenn followed the recommendations of some circle track racers and used leaf springs in the rear suspension.

Although the car packed a mighty Hemi block, Glenn hadn’t kept a close eye on the weight of the components during the construction period. When the car debuted in 1978, the truth became clear.

“The first time it was weighed,” he recalls, “I realized it was heavy. There was a big crowd of other racers and crew around it, and they weren’t worried when they saw it was 3400 pounds.”

That car never really hit its stride, but Glenn was already working on next year’s car. Keeping the weight down would be a priority.

Light Metal

The minimum weight for Glenn’s class was 2250 pounds; even with the powerful V8 under the hood, he’d need a car that was about 1000 pounds lighter than his first creation.

Then he recalled the Old Yeller II. This famous race car wasn’t the most beautiful or elegant creation on track, but it could beat the Jaguars and Maseratis due to its big-displacement engine and low weight. “The power-to-weight [ratio] is essential,” Glenn explains. “Every time you turn, accelerate or hit the brakes, it’s constantly affecting you. I knew I needed 800 horsepower and 2500 pounds or so.”

Glenn prototyped his new frame using a collection of balsa wood sticks. He figured the basic dimensions to scale, then started gluing together balsa to see how it would react to loads in various directions.

“The rear cage, I’d set that part on the table,” he says, “and let the front half sit off the desk.” Then he’d simulate suspension forces by pushing up and down on his mock-up.

“I was trying to use as few tubes as possible,” he explains. “Parallelograms are a big no-no. It’s a good way to triangulate something and see what the stiffness would be.” Once he’d removed all the unnecessary sticks and conjured a solid base tube structure, Glenn transferred the idea to full-scale steel.

The IMSA rules required the whole central section of the donor car to remain intact, but they never specifically mentioned anything about erosion. Glenn bought a 30-gallon drum of pure sulfuric acid, set the whole Challenger central section on a hill, and mopped down the bodywork with acid every day for two weeks.

“I had a bucket of fresh water with some rags to throw on me in case I got any on me,” he chuckles. “It would burn in about a second.” The acid diet ate 35 pounds off the metal, and when he paired it to his balsa-prototyped steel cage, the combination weighed just 320 pounds.

Glenn fabricated the body panels out of fiberglass and aluminum, aiming for an aerodynamic front-end shape reminiscent of a watermelon. The idea was to have minimal disturbances or openings.

In IMSA trim, the car actually carried its radiators in the back to shift the weight slightly to the rear. The setup also cleaned up the front end from a drag perspective.

Glenn devised several front-end treatments for the car, and he was proud of the low drag he achieved. In a 1979 race, despite being saddled with a relatively small 396-cubic-inch Hemi on loan from Chrysler, the Challenger was able to peg 190 mph around Daytona.

There was promise of some solid factory backing for Glenn’s creation, but Chrysler’s financial meltdown in 1979 meant that his timing couldn’t have been worse. Though he and co-driver Phil Currin scored a class win and a fifth overall at the Lumbermens 500-mile race at Mid-Ohio in 1979, the sponsorship dollars were drying up. Glenn was down on money, and after devoting his spare time to racing and building IMSA GT cars during 60-hour work weeks, he was low on energy, too. In 1980, he decided to put the Challenger in mothballs.

Return of the Torque

A quarter of a decade passed, and in that time Glenn had become a logger and lumberman who occasionally autocrossed. An upswing in the popularity of historic racing, combined with his Challenger’s nearly 30-year-old vintage, inspired Glenn to take the car out of storage and set it loose on the track for the 2005 season. As Glenn puts it, “I’m getting old, you know? If I don’t do this soon, I’ll never do it.”

He fitted one of his earlier, less-modified bodies to the car for product identity purposes—his later IMSA bodies had more in common with “Mad Max” than a stock Dodge Challenger—and fitted a conventional front radiator in lieu of the earlier setup.

He was able to replace the problematic Chrysler four-speed gearbox with a proper competition unit from G-Force Racing. Glenn says the new box is simply marvelous. A custom three-puck Quarter Master clutch setup is a match for the Hemi’s prodigious power and the generous grip provided by massive Avon racing slicks.

In his first few years of vintage racing, Glenn sampled a handful of different carburetor setups—some fancy drag-spec Holleys granted good power, but they couldn’t handle the corners. A fellow Challenger owner was selling a car featuring Webers atop a special manifold, but the price for the entire machine was too high. Glenn let the seller know that if the car were ever parted out, he would be interested in the carburetor setup.

A few years later, Glenn purchased that rare manifold for just $150. He fitted a quartet of 48IDA Webers that were modified to 58mm by Gene Berg, and the new setup resulted in a jump of nearly 100 horsepower.

At the 2009 Ultimate Track Car Challenge, the Challenger weighed 2600 pounds without driver. The car’s Hemi was bored and stroked to 572 cubic inches—that’s nearly 9.4 liters—and churned out 862 horsepower and 802 lb.-ft. of torque at the crank. Those figures came at a relatively lazy 6200 rpm.

Glenn insists that the cam profile was costing him about 100 horsepower. He says it’s the first big Hemi he’s ever had that doesn’t vibrate, a trait he attributes to the TCI Rattler mechanical vibration absorber on the crankshaft. He runs a 50/50 mix of 90-octane street gas and 110-octane race fuel.

The Challenger can blast to nearly 100 miles per hour in the first of its four gears, and the acceleration curve and top speed around VIR is mind-boggling for a seemingly massive 1970s muscle car. Phil Currin turned a 1:53.652 fast lap in the UTCC competition on the way to a class win. That time compares nicely with those of today’s Grand-Am Rolex GT machines, cars that usually don’t come from such humble origins. Stunning in-car video from one of Phil’s fastest laps, complete with Traqmate data, can be viewed here:

Ever Evolving

Although Glenn had his good friend Phil drive the car at the 2009 UTCC, he’s itching to get back behind the wheel of his own creation. After a few physical ailments, including a torn rotator cuff, 60-year-old Glenn is exercising regularly and has changed his diet to promote better health. “I’ve lost 40 pounds since last year,” he reports proudly. “I’ve got the resting figured out now. I used to go for 16 hours a day; now it’s 12.”

For the 2010 Pirelli Ultimate Track Car Challenge, Glenn is hoping to have the car back to its lighter rear-radiator setup, complete with one of his more radical downforce-promoting front-end treatments. A loss of 200 pounds and some more aero grip could nudge the Challenger even closer to the 1:50 barrier.

Whatever the result will be, Glenn’s old-school monster Dodge doesn’t really need to prove anything. It was one of the coolest cars at the 2009 UTCC even when it was standing still in the paddock. The fact that it was able to run with and defeat nearly every other car in the event is a testament to Glenn’s clever home-brewed engineering, Phil’s bravery and skill as a driver, and the magic of a great big torquey Hemi V8.

This article is from an old issue of Grassroots Motorsports. Get all the latest how-tos and stories for just $20 a year. Subscribe now.

I love this car, the in car noises would make me never want to get out of it. Getting to work with "Fast" Phil with our challenge car 2 years ago was a riot! Talk about a guy who is totally approachable, and down to earth. Amazing.

Spinout007 wrote:
I love this car, the in car noises would make me never want to get out of it. Getting to work with "Fast" Phil with our challenge car 2 years ago was a riot! Talk about a guy who is totally approachable, and down to earth. Amazing.

Yep. I was honored that a guy who does events where he his speeds top 170mph and rarely drop past 60mph got a kick out of driving a lightly turboed Miata around a parking lot.

I think I saw 2nd gear deliver 55 to 120 mph, and I believe this is the first time I've ever witnessed a tach move slower than the speedometer. way slower. I suppose the audi diesels that ran endurance a couple years ago did that but I never saw it.

thanks: “Carolyn, my wife of 36 years, and children Gregory, Julia and Lisa. The people at VIR have all been really, really nice. It’s like going to another planet—it takes a week to come back down to earth once you get home.”